Direct curve editing

In modules such as AssaySynthesis the Property Profile graph is calculated using the advanced modelling tools included in Assay. If you modify any of the data included in your assay by changing values in the measurement grid or through Editing Mode, when you regenerate the crude the Property Profile graph will update to reflect your changes. Using guide points you can modify the shape of the Property Profile graph, but the underlying model still controls the appearance of the curve. See Guide points.

By converting the Property Profile graph to a spline representation you can obtain complete control of the shape of the curve. This may be useful when you want to supplement the output of Assay and guide points do not give you enough control. Using a spline representation you obtain complete control of the shape of the Property Profile graph, enabling you to use your experience of crudes to closely direct results.

To use direct curve editing and convert the property profile to a spline curve you must enable Spline Curve editing in the Preferences dialog. See Generation module options.

After generation you can convert any modelled Property Profile curve to a spline, even if you did not enter measurement data for that property. To convert a Property Profile to a spline make sure the correct crude is selected and click Spline Representation either in linear mode or in logarithmic mode . You can undo your changes later by selecting Model Representation which will use the model description of the property, losing any changes you have made. Only the currently selected property is converted to a spline curve, other properties are still represented by their modelled profiles. To convert other properties to a spline curve select the property using the Graph Property Selector and then click Spline Representation.

Control points on your spline curve are represented by blue dots on the curve. To change the position of a control point use the Edit Point tool . After you move a point the curve will instantly update and the modelled values in the measurement grid will update to reflect the change. To add more points and get finer control of the curve use the Add Point tool . Remove any unnecessary point using the Remove Point tool .

If Uncertainty Estimates are shown on the graph for the property and it is converted to a spline curve the error bars are removed.

Copy property curves from another crude

Normally when using direct curve editing control points are defined by the user to define the shape of the property profile. It is also possible to copy an existing assay's property profile to the current assay to use as a source of the direct curve.

For example, if working up an assay of Arab Light the user might believe that the particular sample had a sulphur profile closer to that of Arab Extra Light. The user might then copy the sulphur property profile of an Arab Extra Light assay to the current assay, overwriting any model based property.

To copy the property profile from a Database assay to the current assay select Copy Property Curve from Crude... from the Property Profile graph context menu. This opens the Select Crude dialog which allows the source of crude data to be chosen from the existing Database assays. See Select crudes.